The process of apoptosis plays an important role in embryonic development, immune function, tissue homeostasis and cancer surveillance. Understanding the molecular mechanisms that underlay apoptosis should have a significant impact on therapies for such diverse disorders as heart failure, cancer chemotherapy, and cerebrovascular events. To date, two broad pathways have been defined: an intrinsic pathway that depends on integrating death signals at the mitochondrial outer membrane in response to a variety of triggers, including ER stress, and an extrinsic pathway that relies on signals from the plasma membrane but also involves amplification of the signal via mitochondria. There is both a signaling mechanism involving a number of pro- and anti-apoptotic proteins and a bioenergetic mechanism involving a protein complex composed of mitochondrial outer membrane, inner membrane and matrix compartment proteins termed the mitochondrial permeability transition pore (MPTP). This proposal addresses the role of channel proteins of the mitochondrial outer membrane;Voltage dependent Anion Channels, and specifically VDAC2, in altering mitochondrial permeability, interacting with pro-apoptotic proteins such as BAK, and in the activation of apoptosis. We hypothesize that mitochondrial permeability at the outer membrane (VDACs) and across both the inner and outer membranes (MPTP) both regulates aspects of apoptosis and normal physiology. Specific aim 1 will determine the role of VDAC2 in regulating pro-apoptotic protein subcellular location and function. Specific aim 2 will define the components of the MPTP in genetically engineered cultured cells. Specific aim 3 will examine the in vivo functions of VDAC2 in apoptosis using gene targeted mice. These studies will help determine how mitochondrial permeability acts to regulate both physiologic and pathophysiologic cellular events, and validate the proteins as potential therapeutic targets in a variety of disease states. PUBLIC HEALTH RELEVANCE: The goal of this project is to determine the role of channel proteins found in the mitochondrial outer membrane in the activation and control of cell death, a highly regulated process that has a crucial role in normal development, control of infections, and avoidance of cancer in mammals, including humans. Using genetic and biochemical techniques, in combination with genetically engineered cultured cells and mice, the aim is to establish that these channels are potential targets for therapeutic interventions.